Instantaneous recording phonographic disks



Patented Aug. 19, 1952 INS TAN TAN E'OUS RECORDING PHONO- GRAPHIC DISKS George M. Sutheim, Jamaica, N. Y.,, assignorto Audio Devices, Inc., New-York, N. Y., a corporation of New York No Drawing. Application August-26, 1948, Serial No. 46,355

12 Claims.

This invention relates to phonographic discs of the instantaneous play-back type and has for its object certain improvements in the method of producing such discs, in the discs themselves as an article of manufacturain the method of producing the recording lacquer, and in the recording lacquer itself as an article of" manufacture.

Phonographic discs of the instantaneous playback type are formed of a base, such as metal, glass, paper, etc., coated with a recording lacquer. The recording lacquers are made in general of mixtures of cellulose esters or ethers, solvents, plasticizers and dyes. Although various formulae are employed, a typical one is 33.3% of sec. nitrocellulose; 18.0% wetting alcohol; 28.2% ethyl acetate; 10.0% dibutyl phthalate;10.0% castor oil; and 0.5% dye. The'coating is dried, by the extraction of volatile solvent, to produce a smooth and uniform surface on the resulting blank phonographic disc. The relatively soft coating on theblank disc is adapted for the cutting. of sound grooves or tracks therein by a suitable sound recording or; cutting stylus, after which the discs may be played back instantaneously by the use of a suitable sound reproducing point.

the noise level, referred to as climbing. When sound grooves are cut in thedisc in humid weather, they appear normal and shiny at first. As the cutting progresses, the grooves change their appearance, they become dull and. gray. This change in appearance, of little importance by itself, is invariably acompanied by an increase in noise level. When played back the discs sound noisy to such an extent that the recordings become practically useless.

Since a similar effect can be obtained by using a defective cutting stylus, it is probable that minute coating particles-far below visibilityadhere to the stylus, which thereupon becomes rough and in turn produces rough and noisy sound grooves. In fact, gentle polishing of the stylus apparently removes the adhering particles, whereupon the cutting proceeds well for a few revolutions; after a short while, however, climbi ing sets in again.

It is, of course, highly desirable from the view point of the user that blank phonographicdiscs of the, instantaneous play-back type be usable under the most adverse weather conditions withoutany substantial deterioration in quality,'particularly with respect to noise level. That the production: of such blank discs is of utmost importance to the manufacturer goes without saying, because otherwise his output is considered faulty, and results in a great deal of customer complaints as wellas loss of business.

My investigations have led to the discovery that ifa suitable agent is added to and dispersed widely throughout the recording lacquer, before it" is applied to the base as a coating, the disadvantages just mentioned are for the most part overcome. The objectionable climbing may be entirely or. at least substantially eliminated so that recordings may be made during humid weather without an undue increase in noise level. The special ingredient added to the recording lacquer has'a modifying efl'ect on the disc coating, the mechanism. of which is not fully understood. The ingredient may be referred to conveniently as a modifying or anti-climbing agent.

As will be seen from the following; description, the invention resides in the recording lacquers and the blank'phonographic discs, as an article of manufacture.

From the standpoint of the record-ing lacquer per se for the-coating of blank phonographic discs of the instantaneous play-back type, the invention involves a lacquer 'base having a very finely divided inert pigment widely dispersed therein in amount to inhibit climbing when the lacquer forms a coating on a blank phonographic disc and a sound groove is cut in the coating with a sound recording-or cutting stylus.

As far as the phonographic disc per se of the instantaneous play-back type is concerned, the invention comprises a base coatedwith a recording lacquer containing very finely divided inert pigmentwidely dispersed therein, the pigment being present in amount to inhibit climbing when a sound groove is cut in the coating with a sound recording or cutting stylus.

As already noted, it is customary in this art to employ as a recording lacquer a mixture of cellulose esters or ethers, solvents, plasticizers, and dyes. Each ingredient functions in its intended manner; The cellulosic compounds in large part form the body of the lacquer; The solvents render them soluble for the coating operation. The plasticizers contribute to the pliability of the coatings when the solvents have been extracted in the drying and curing operations. The dyes contribute the desired color. While a variety of dyes may be employed, the one most extensively used is a soluble dye to impart a dark color to the lacquer and hence to the coating on the phonographicv disc. Relatively small amounts of the dye are required. The cellulosic esters or ethers, solvents and'plasticizersvary somewhat in relative amounts, depending to a large extent on the reactions that would impair the quality of the blank phonographic discs for recording. The field of pigments is, of course, large and some of them have marked reactive characteristics, which render them unfit for use in the practice of the invention. There are neutral pigments, however, that are adapted for the practice of the invention and are for that reason included herein. Among such pigments are calcium carbonate, colloidal silica, lithol red, carbon black, phthalocyanineblue, and precipitated yellow iron oxide. These pigments are mentioned only by way of example, and for that reason they do not, nor are they intended to, exhaust the list of pigments available for the purpose of preventing or inhibiting climbing. The pigments contemplated include finely divided inert particles of any material capable of inhibiting climbing, whether or not they 4 whether a given pigment is suitable for the purpose.

In illustration of the invention, the following examples may be referred to. To an ordinary recording lacquer, such as is used in the art, and

.which is satisfactory in dry weather so far as climbing is concerned, a number of inert pigments were incorporated in very small amounts and finely dispersed. Among the pigments were calcium carbQnate, colloidal silica, Lithol red, carbon black, phthalocyanine-blue and precipitated yellow iron oxide. The pigment was, and is preferably, added in the form of a suitable dispersion to the recording lacquer after which the mixture itself was thoroughly mixed. Separate recording lacquers specially prepared in this manner, along with an untreated recording lacquer as a control, after being coated on a base, were dried and cured in the normal routine fashion. The resulting blank phonographic discs were then placed in a humidity chamber with simulated summer conditions and exposed to this atmosphere for specified periods. As will be seen from the table below, sound grooves were cut in each disc during dry weather and also after each disc Was exposed to the simulated humid summer impart opacity to the recording lacquer. weather for l-week and for 3-weeks. The results Since sound grooves or tracks are to be cut in are set out in the following table:

Climbing Dis ersion Added of Particle Size inm Humid Remarks 7 p Dry mer Weather 1 Weather l-week 3-weeks 1 up 16 up 25 Deleterious Climbing.- Example 1.. Calcium Carbonate 0 0 Full Protection. Example 2 0.10% Colloidal Silica.-. 10-30 0 0 0 Do. Example 3.- 1 0.05% Colloidal Silica 10-30 0 0 0 Do. Example 4 0 0 0 130. Example 5 f 0 up 3 up 7 Partial Protection. Example 6 13 0 0 0 Full Protection. Example 7 l3 0 up 2 up 5 Partial Protection. Example 8 7 0 up 4 up 7 Do. Example 9 d recipi- 100 0 0 0 Full Protection.

tate Example 10 1. 1.00% Methyl Violet Soluble Dye. Molecular Range 0 up 16 up Deleterious Climbing.

1 i. e. 90 F. :l=2 and 80%1:l:5% Relative Humidity.

the coatings of the blank phonographic discs, the particle size of the pigment should'not be sufficiently large of and by itself substantially-to raise the noise level. My investigations also clearly indicate that the particle size may be too small efiectively to prevent or inhibit climbing. The particles used must be very small, that is, in the lower limits of the colloidal range, preferably between about 10 and millimicrons in size. Particles in the upper limits of the colloidal range or larger, as just noted, cannot be used due to their coarseness. It may be pointed out, however, that even discs coated with a recording lacquer containing the coarser particle size pigment, which therefore have an initial high noise level, do not show any substantial climbing when sound grooves are cut therein in humid weather. It is obvious, however, that it is impractical to use a pigment of such coarse or large particle size that itcontributes a high noise level on its own account, quite apart from any climbing due to humid weather. Exceedingly small particles, such as those in a state of molecular dispersion, lose their effectiveness. For practical purposes, an optimum particle size appears to be in the vicinity of 10 millimicrons. In View of the present disclosures, one skilled in the art need only make a simple trial and error test to determine Referring to the table, it will be noted thatthe column to the left identifies the examples. The first one is referred to as Control, meaning an ordinary coating of recording lacquer not containing pigment. Examples 1 to 10 inclusive refer to coatings of recording lacquers containinga pigment, the name of the pigment and the percent by weight employed being set out in the second column headed Dispersion added of." The thirdcolumn gives the particle size of the pigment in millimicrons, so far as this data is available. The next three columns relate to Climbing, the first of the three referring to the observations in Dry weather and the remaining two columns to the observations during simulated Humid summer weather, one of the latter columns being directed to the observations after l-week and the other column after 3-. weeks. In other words, sound grooves were cut in each disc during dry weather and also after exposure in simulated humid summer weather for l-week and 3-weeks, respectively. The last column is headed Remarks and a notation is made for each example, to point out the efiect on climbing,

Going back to the Control example at the top of the list, it will be noted that no dispersion of pigment was added, the space for particle size,

weather conditions.

weather: indicatesthat-there was no :cliin'bing;

The legend up 16" under '1 -week? "andthe legend'fup 25--under 3-week's;indicate the amount of climbing that occurred --These figures ref or tea raisein" noise levelwhich in recordingpractice is denoted in db, decibels. The-figures 16' and "25, therefore, indicate-a substantial risein noise level andyas' is to-be expected; the-Temark for this example-isDeleterious climbing 7 Example 1 refers to theuseof 0 .10 ca-lcium carbonate having a particlesi'zeof '50"-m'illimicrons. Whilefasnoted'above; such aparticle size of and by itself introduces an'- undesirable noise level, the values' set -out in'the: three d-ifi'erent columns for climbing, however, indicate that there was" no climbing; which isin"tu'rn' referred 'to-as Full protection in the column Remarks.

Examples 2'and3'refer'to the use of 0.10% and 0.05%? respectively; of colloidal silica. having a ran e of -30 millimicrons. Thezero-mark in each of three columns under fClimbing, indicates that due to the presence of the pigment there was no,.clirnbing in dry weather or after 1-week*and 3"-.w.eeks of' exposure to "humid, summer weather; and'the. following remark-Full protection? in the lastcolunin indicates as muchf It will fbe noted that although twice 'asmuclf'of this pigmentiwas used; ir'roneexampleas-in-th ther, the same beneficial resultswere'observedz' Examples 4andi5fsliow the:.use='of 0.25% and 0.10%., of Lithol red, respectively, of unknown specific particle size, although presumably; within the range herein contemplated." In the case of Example 4, with the larger amount of pigment,

there was no climbing in dry weather, or under humid summer weather for l-week and 3-weeks, so that the legend Full protection is to be found, as expected, in the last column. In the case 01' Example 5, however, with substantially less, half as much, pigment, the noise levels are up 3? for l-week and up '7" for 3-weeks of humid summer weather, so that the legend quite properly is Partial protection. It is evident that the optimum amount to use may be determined readily by simple tests.

Examples 6 and '7 cover the use of carbon black as the modifying or anti-climbing agent, the particle size being 13 millimicrons. As in all of the examples, no climbing was found under dry In example 6-, the carbon black amounted to 0.10% and no climbing was observed under the 1-week and the 3-weeks humid summer weather tests, so that Full protection is reported. In example '7 only half as humid-summer weathen' 7 6 theremark Full protection? The ini-tiar'noi'se" level, however; was ob'jectionable. Example 10,- on the other-hand; illustrates-the use of '1.00'%methyl violet soluble dye tllith apar-j ticle size within the molecular-range wilifb'e noted that the results are precisely thefsa'me as those reported in the Controlexample;"- na mely, up; 16-" for T-Week and" u for 3 weksbf It willthus beflseen that'thereis considerable latitude the choice-of pigments-so "far as tn elimination of "climbing; is "concerned; Carborr black is; thepresently preferred 'pigment'bcause' it is readily obtainable in" the form off-aprepared M or eliminated because the carbon black use 20' dispersion which may be easily added to:- and readily mixed with the recording -la'c vque' er W ilel h s-i isme im ytbc u edy th qu' f c n a n 1 i ei the e. a

prevent or inhibit climbi g darken-Vs? Although it is.wel1- v v pIgments"maS* be andj are .frequently added in' substantial amounts to ordinary lacquers to give them" the desiredcolor, those engaged in the instantaneous play-back phonographi-e d'iscf'industryfh been very careful" to keep yfron slicl} 1 56 fpigmerits in their recording, lacquersiffl'heyi have few that" th incorporationof, pigmentsfin their recordingfllacquers is merely another way ofl'a'dd inglt'oj their troubles, Lbecau 't merely meansjthe in orp ration fin'oi r ucin s l d' i..-a1 d% .0r thatj -reason. unusual precautions aref taken to eliminate o s-twat m r- P 'en ma if in recording lacquers; quite'apart, fromthefact that pigment solids are not added: "Io'this""ei'1d' the recording lacquers are successively pressurefiltered to insure a coating material that will be free of solids and which, therefore, will keep down the noise level of the disc coating. As a' part of this intensive program to keep solids out 7 of the recording lacquers, dyes alone are emmuch carbon black, namely 0.05%, was used in recording lacquer, and different results were obtained. The noise levels were up 2 for l-week and up 5 for 3-weeks, thus showing Partial protection. These examples indicate that some discretion should be exercised in determining the amount of carbon black pigment to be used, but show that the optimum amount is easily found.

Example 8 shows the use of 0.25% phthalocyanine-blue of unknown specific particle size. The noise level figures are up 4 and "up '7 for the two standard humid summer weather tests of l-week and 3-weeks, respectively; so that Partial protection" is noted. Used in different amount, this pigment would undoubtedly show a different result.

Example 9 illustrates the use of 0.10% relatively coarse precipitated yellow iron-oxide, with no climbing found in any of the tests and hence ploy-ed to impart the desired colors. They .pass through the filters without any trouble and, of course, are not regarded as solids.

My proposal deliberately to incorporate solids in recording lacquers to reduce noise level, when everyone in the industry is deliberately engaged in keeping them out at all costs to reduce noise level, is regarded as sheer heresy. I have found, much to my surprise and that of my colleagues, that a judicious use of solids, in the form of pigments, is possible, and that such solids do not increase, but on the contrary decrease, noise level when-recording under humid summer weather conditions.

The presence of the pigment solids per se in the unfiltered recording lacquer is not disadvantageous because their particle size permits ready passage through the filters, while the customary solids found in the recording lacquer are held back. The presence of the pigment solids in the filtered recording lacquer is not disadvantageous because the coating operation is not in any Wise impaired.

As has been shown, the presence of the pi ment solids in the disc coating is a decided 'advantage when recording under humid summer weather conditions. -A further advantage is that the presence of the pigment particles in the disc coating does not increase the noise level when recording under dry Weather conditions. In other words, a disc with the improved coating of the invention may be stored indefinitely and may be used readily under dry or humid weather conditions with no rise innoise level. This-is of: considerable importance tor-the industry- IIQ; one skilled in this art, it will be clear that the pliactice of the inventionreadily. -1ends itself tonumerous modifications p of pnly a fraction of one per cent and beinginert to V theningredients of the recording. lacquer to prevent chemical reactions that would impair the qualityo;f..-the blank, phonographic disc for rewr a i T I =2. A phonographicdisc' according to claim l in which the pigment is carbon black. 7 I t 3. A phonographicdisc according to claim 1 in which the pigment is calcium carbonate. 7 Q5 Aphonographic disc according to claim 1 in which, the pigment is. colloidal silica. Y 7 I 5., A phonographic discaccordin'g to claim 1 in which the pigmentis Lithol red.

, 6. A phonographic disc according to claim 1 in which the pigment ,is' phthalocyanine-b-lue. $7.115 recording lacquer, for coating phonographic discs of theinstantaneous play-back type comprising jl'a lacquer base having incorporated therein 'an inert pigment to inhibit climbing when a sound groove is cut in the-coating with a sound recording or cutting stylus, said pigment having a particle size between about 1 0 and- 0 millimicrons, being present in the lacquen-base to theextent ofoonly a fraction of one per cent and being inert to the ingredients of the lacquer base to prevent chemical reactions. that would impair'the quality of the lacquer for recording pu po e -z v 3 f 1 8. A recordinglacquer according toclairnfl in whichthe pigment is carbon black. 9. A recording lacqueraccording toclaim '-7- in which the pigment is calcium carbonate.

0 10; -A recording lacquer accord ing to claim Tin which the pigmentis colloidal silica.

e 11. A recording lacquer according to claim '7 in which the pigment is Lithol red. h a j '12. A recording lacqueraccording to claim l -in whichbhe'pigment is phthalocyanine-blue; V 1 GEORGE M., SU'IHlElIlVl REFERENCES errati- The following references are 'of record" in'the file of this-patent: r l STATES PAT NTS Date, 

1. A PHONOGRAPHIC DISC OF THE INSTANTANEOUS PLAY-BACK TYPE COMPRISING A BASE, A COATING OF A PRESSURE-FILTERED LACQUER ON THE BASE, SAID LACQUER COATING CONTAINING AN INERT PIGMENT DISPERSED THEREIN TO INHIBIT CLIMBING WHEN A SOUND GROOVE IS CUT IN THE COATING WITH A SOUND RECORDING OR CUTTING STYLUS, SAID PIGMENT HAVING A PARTICLE SIZE BETWEEN ABOUT 10 AND 50 MILLIMICRONS, BEING PRESENT IN THE LACQUER COATING TO THE EXTENT OF ONLY A FRACTION OF ONE PER CENT AND BEING INERT TO THE INGREDIENTS OF THE RECORDING LACQUER TO PREVENT CHEMICAL REACTIONS THAT WOULD IMPAIR THE QUALITY OF THE BLANK PHONOGRAPHIC DISC FOR RECORDING. 